/*
 * @Author: cpu_code
 * @Date: 2020-07-12 19:24:49
 * @LastEditTime: 2020-07-18 16:37:08
 * @FilePath: \Android系统源代码情景分析（第三版）程序文件\chapter-4\src\system\core\init\devices.c
 * @Gitee: https://gitee.com/cpu_code
 * @Github: https://github.com/CPU-Code
 * @CSDN: https://blog.csdn.net/qq_44226094
 * @Gitbook: https://923992029.gitbook.io/cpucode/
 */ 
/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <fcntl.h>
#include <dirent.h>
#include <unistd.h>
#include <string.h>

#include <sys/socket.h>
#include <sys/un.h>
#include <linux/netlink.h>
#include <private/android_filesystem_config.h>
#include <sys/time.h>
#include <asm/page.h>
#include <sys/wait.h>

#include <cutils/uevent.h>

#include "devices.h"
#include "util.h"
#include "log.h"
#include "list.h"

#define SYSFS_PREFIX    "/sys"
#define FIRMWARE_DIR1   "/etc/firmware"
#define FIRMWARE_DIR2   "/vendor/firmware"

static int device_fd = -1;

struct uevent {
    const char *action;
    const char *path;
    const char *subsystem;
    const char *firmware;
    const char *partition_name;
    int partition_num;
    int major;
    int minor;
};

static int open_uevent_socket(void)
{
    struct sockaddr_nl addr;
    int sz = 64*1024; // XXX larger? udev uses 16MB!
    int on = 1;
    int s;

    memset(&addr, 0, sizeof(addr));
    addr.nl_family = AF_NETLINK;
    addr.nl_pid = getpid();
    addr.nl_groups = 0xffffffff;

    s = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
    if(s < 0)
        return -1;

    setsockopt(s, SOL_SOCKET, SO_RCVBUFFORCE, &sz, sizeof(sz));
    setsockopt(s, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));

    if(bind(s, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
        close(s);
        return -1;
    }

    return s;
}

struct perms_ {
    char *name;
    char *attr;
    mode_t perm;
    unsigned int uid;
    unsigned int gid;
    unsigned short prefix;
};

struct perm_node {
    struct perms_ dp;
    struct listnode plist;
};

static list_declare(sys_perms);
static list_declare(dev_perms);

int add_dev_perms(const char *name, const char *attr,
                  mode_t perm, unsigned int uid, unsigned int gid,
                  unsigned short prefix) {
    struct perm_node *node = calloc(1, sizeof(*node));
    if (!node)
        return -ENOMEM;

    node->dp.name = strdup(name);
    if (!node->dp.name)
        return -ENOMEM;

    if (attr) {
        node->dp.attr = strdup(attr);
        if (!node->dp.attr)
            return -ENOMEM;
    }

    node->dp.perm = perm;
    node->dp.uid = uid;
    node->dp.gid = gid;
    node->dp.prefix = prefix;

    if (attr)
        list_add_tail(&sys_perms, &node->plist);
    else
        list_add_tail(&dev_perms, &node->plist);

    return 0;
}

void fixup_sys_perms(const char *upath)
{
    char buf[512];
    struct listnode *node;
    struct perms_ *dp;

        /* upaths omit the "/sys" that paths in this list
         * contain, so we add 4 when comparing...
         */
    list_for_each(node, &sys_perms) {
        dp = &(node_to_item(node, struct perm_node, plist))->dp;
        if (dp->prefix) {
            if (strncmp(upath, dp->name + 4, strlen(dp->name + 4)))
                continue;
        } else {
            if (strcmp(upath, dp->name + 4))
                continue;
        }

        if ((strlen(upath) + strlen(dp->attr) + 6) > sizeof(buf))
            return;

        sprintf(buf,"/sys%s/%s", upath, dp->attr);
        INFO("fixup %s %d %d 0%o\n", buf, dp->uid, dp->gid, dp->perm);
        chown(buf, dp->uid, dp->gid);
        chmod(buf, dp->perm);
    }
}

static mode_t get_device_perm(const char *path, unsigned *uid, unsigned *gid)
{
    mode_t perm;
    struct listnode *node;
    struct perm_node *perm_node;
    struct perms_ *dp;

    /* search the perms list in reverse so that ueventd.$hardware can
     * override ueventd.rc
     */
    list_for_each_reverse(node, &dev_perms) {
        perm_node = node_to_item(node, struct perm_node, plist);
        dp = &perm_node->dp;

        if (dp->prefix) {
            if (strncmp(path, dp->name, strlen(dp->name)))
                continue;
        } else {
            if (strcmp(path, dp->name))
                continue;
        }
        *uid = dp->uid;
        *gid = dp->gid;
        return dp->perm;
    }
    /* Default if nothing found. */
    *uid = 0;
    *gid = 0;
    return 0600;
}

static void make_device(const char *path,
                        const char *upath,
                        int block, int major, int minor)
{
    unsigned uid;
    unsigned gid;
    mode_t mode;
    dev_t dev;

    mode = get_device_perm(path, &uid, &gid) | (block ? S_IFBLK : S_IFCHR);
    dev = makedev(major, minor);
    /* Temporarily change egid to avoid race condition setting the gid of the
     * device node. Unforunately changing the euid would prevent creation of
     * some device nodes, so the uid has to be set with chown() and is still
     * racy. Fixing the gid race at least fixed the issue with system_server
     * opening dynamic input devices under the AID_INPUT gid. */
    setegid(gid);
    mknod(path, mode, dev);
    chown(path, uid, -1);
    setegid(AID_ROOT);
}

#if LOG_UEVENTS

static inline suseconds_t get_usecs(void)
{
    struct timeval tv;
    gettimeofday(&tv, 0);
    return tv.tv_sec * (suseconds_t) 1000000 + tv.tv_usec;
}

#define log_event_print(x...) INFO(x)

#else

#define log_event_print(fmt, args...)   do { } while (0)
#define get_usecs()                     0

#endif

static void parse_event(const char *msg, struct uevent *uevent)
{
    uevent->action = "";
    uevent->path = "";
    uevent->subsystem = "";
    uevent->firmware = "";
    uevent->major = -1;
    uevent->minor = -1;
    uevent->partition_name = NULL;
    uevent->partition_num = -1;

        /* currently ignoring SEQNUM */
    while(*msg) {
        if(!strncmp(msg, "ACTION=", 7)) {
            msg += 7;
            uevent->action = msg;
        } else if(!strncmp(msg, "DEVPATH=", 8)) {
            msg += 8;
            uevent->path = msg;
        } else if(!strncmp(msg, "SUBSYSTEM=", 10)) {
            msg += 10;
            uevent->subsystem = msg;
        } else if(!strncmp(msg, "FIRMWARE=", 9)) {
            msg += 9;
            uevent->firmware = msg;
        } else if(!strncmp(msg, "MAJOR=", 6)) {
            msg += 6;
            uevent->major = atoi(msg);
        } else if(!strncmp(msg, "MINOR=", 6)) {
            msg += 6;
            uevent->minor = atoi(msg);
        } else if(!strncmp(msg, "PARTN=", 6)) {
            msg += 6;
            uevent->partition_num = atoi(msg);
        } else if(!strncmp(msg, "PARTNAME=", 9)) {
            msg += 9;
            uevent->partition_name = msg;
        }

            /* advance to after the next \0 */
        while(*msg++)
            ;
    }

    log_event_print("event { '%s', '%s', '%s', '%s', %d, %d }\n",
                    uevent->action, uevent->path, uevent->subsystem,
                    uevent->firmware, uevent->major, uevent->minor);
}

static char **parse_platform_block_device(struct uevent *uevent)
{
    const char *driver;
    const char *path;
    char *slash;
    int width;
    char buf[256];
    char link_path[256];
    int fd;
    int link_num = 0;
    int ret;
    char *p;
    unsigned int size;
    struct stat info;

    char **links = malloc(sizeof(char *) * 4);
    if (!links)
        return NULL;
    memset(links, 0, sizeof(char *) * 4);

    /* Drop "/devices/platform/" */
    path = uevent->path;
    driver = path + 18;
    slash = strchr(driver, '/');
    if (!slash)
        goto err;
    width = slash - driver;
    if (width <= 0)
        goto err;

    snprintf(link_path, sizeof(link_path), "/dev/block/platform/%.*s",
             width, driver);

    if (uevent->partition_name) {
        p = strdup(uevent->partition_name);
        sanitize(p);
        if (asprintf(&links[link_num], "%s/by-name/%s", link_path, p) > 0)
            link_num++;
        else
            links[link_num] = NULL;
        free(p);
    }

    if (uevent->partition_num >= 0) {
        if (asprintf(&links[link_num], "%s/by-num/p%d", link_path, uevent->partition_num) > 0)
            link_num++;
        else
            links[link_num] = NULL;
    }

    slash = strrchr(path, '/');
    if (asprintf(&links[link_num], "%s/%s", link_path, slash + 1) > 0)
        link_num++;
    else
        links[link_num] = NULL;

    return links;

err:
    free(links);
    return NULL;
}

static void handle_device_event(struct uevent *uevent)
{
    char devpath[96];
    int devpath_ready = 0;
    char *base, *name;
    char **links = NULL;
    int block;
    int i;

    if (!strcmp(uevent->action,"add"))
        fixup_sys_perms(uevent->path);

        /* if it's not a /dev device, nothing else to do */
    if((uevent->major < 0) || (uevent->minor < 0))
        return;

        /* do we have a name? */
    name = strrchr(uevent->path, '/');
    if(!name)
        return;
    name++;

        /* too-long names would overrun our buffer */
    if(strlen(name) > 64)
        return;

        /* are we block or char? where should we live? */
    if(!strncmp(uevent->subsystem, "block", 5)) {
        block = 1;
        base = "/dev/block/";
        mkdir(base, 0755);
        if (!strncmp(uevent->path, "/devices/platform/", 18))
            links = parse_platform_block_device(uevent);
    } else {
        block = 0;
            /* this should probably be configurable somehow */
        if (!strncmp(uevent->subsystem, "usb", 3)) {
            if (!strcmp(uevent->subsystem, "usb")) {
                /* This imitates the file system that would be created
                 * if we were using devfs instead.
                 * Minors are broken up into groups of 128, starting at "001"
                 */
                int bus_id = uevent->minor / 128 + 1;
                int device_id = uevent->minor % 128 + 1;
                /* build directories */
                mkdir("/dev/bus", 0755);
                mkdir("/dev/bus/usb", 0755);
                snprintf(devpath, sizeof(devpath), "/dev/bus/usb/%03d", bus_id);
                mkdir(devpath, 0755);
                snprintf(devpath, sizeof(devpath), "/dev/bus/usb/%03d/%03d", bus_id, device_id);
                devpath_ready = 1;
            } else {
                /* ignore other USB events */
                return;
            }
        } else if (!strncmp(uevent->subsystem, "graphics", 8)) {
            base = "/dev/graphics/";
            mkdir(base, 0755);
        } else if (!strncmp(uevent->subsystem, "oncrpc", 6)) {
            base = "/dev/oncrpc/";
            mkdir(base, 0755);
        } else if (!strncmp(uevent->subsystem, "adsp", 4)) {
            base = "/dev/adsp/";
            mkdir(base, 0755);
        } else if (!strncmp(uevent->subsystem, "msm_camera", 10)) {
            base = "/dev/msm_camera/";
            mkdir(base, 0755);
        } else if(!strncmp(uevent->subsystem, "input", 5)) {
            base = "/dev/input/";
            mkdir(base, 0755);
        } else if(!strncmp(uevent->subsystem, "mtd", 3)) {
            base = "/dev/mtd/";
            mkdir(base, 0755);
        } else if(!strncmp(uevent->subsystem, "sound", 5)) {
            base = "/dev/snd/";
            mkdir(base, 0755);
        } 
        else if(!strncmp(uevent->subsystem, "misc", 4) &&
                    !strncmp(name, "log_", 4)) 
        {
            //新注册的设备类型为misc，并且设备名称是以“log_”开头的，就会在/dev目录中创建一个log目录
            base = "/dev/log/";
            mkdir(base, 0755);
            // 将设备名称的前四个字符去掉， 即去掉前面的“log_”子字符串
            name += 4;
        } else
            base = "/dev/";
    }

    if (!devpath_ready)
        snprintf(devpath, sizeof(devpath), "%s%s", base, name);

    if(!strcmp(uevent->action, "add")) {
        make_device(devpath, uevent->path, block, uevent->major, uevent->minor);
        if (links) {
            for (i = 0; links[i]; i++)
                make_link(devpath, links[i]);
        }
    }

    if(!strcmp(uevent->action, "remove")) {
        if (links) {
            for (i = 0; links[i]; i++)
                remove_link(devpath, links[i]);
        }
        unlink(devpath);
    }

    if (links) {
        for (i = 0; links[i]; i++)
            free(links[i]);
        free(links);
    }
}

static int load_firmware(int fw_fd, int loading_fd, int data_fd)
{
    struct stat st;
    long len_to_copy;
    int ret = 0;

    if(fstat(fw_fd, &st) < 0)
        return -1;
    len_to_copy = st.st_size;

    write(loading_fd, "1", 1);  /* start transfer */

    while (len_to_copy > 0) {
        char buf[PAGE_SIZE];
        ssize_t nr;

        nr = read(fw_fd, buf, sizeof(buf));
        if(!nr)
            break;
        if(nr < 0) {
            ret = -1;
            break;
        }

        len_to_copy -= nr;
        while (nr > 0) {
            ssize_t nw = 0;

            nw = write(data_fd, buf + nw, nr);
            if(nw <= 0) {
                ret = -1;
                goto out;
            }
            nr -= nw;
        }
    }

out:
    if(!ret)
        write(loading_fd, "0", 1);  /* successful end of transfer */
    else
        write(loading_fd, "-1", 2); /* abort transfer */

    return ret;
}

static void process_firmware_event(struct uevent *uevent)
{
    char *root, *loading, *data, *file1 = NULL, *file2 = NULL;
    int l, loading_fd, data_fd, fw_fd;

    log_event_print("firmware event { '%s', '%s' }\n",
                    uevent->path, uevent->firmware);

    l = asprintf(&root, SYSFS_PREFIX"%s/", uevent->path);
    if (l == -1)
        return;

    l = asprintf(&loading, "%sloading", root);
    if (l == -1)
        goto root_free_out;

    l = asprintf(&data, "%sdata", root);
    if (l == -1)
        goto loading_free_out;

    l = asprintf(&file1, FIRMWARE_DIR1"/%s", uevent->firmware);
    if (l == -1)
        goto data_free_out;

    l = asprintf(&file2, FIRMWARE_DIR2"/%s", uevent->firmware);
    if (l == -1)
        goto data_free_out;

    loading_fd = open(loading, O_WRONLY);
    if(loading_fd < 0)
        goto file_free_out;

    data_fd = open(data, O_WRONLY);
    if(data_fd < 0)
        goto loading_close_out;

    fw_fd = open(file1, O_RDONLY);
    if(fw_fd < 0) {
        fw_fd = open(file2, O_RDONLY);
        if(fw_fd < 0)
            goto data_close_out;
    }

    if(!load_firmware(fw_fd, loading_fd, data_fd))
        log_event_print("firmware copy success { '%s', '%s' }\n", root, uevent->firmware);
    else
        log_event_print("firmware copy failure { '%s', '%s' }\n", root, uevent->firmware);

    close(fw_fd);
data_close_out:
    close(data_fd);
loading_close_out:
    close(loading_fd);
file_free_out:
    free(file1);
    free(file2);
data_free_out:
    free(data);
loading_free_out:
    free(loading);
root_free_out:
    free(root);
}

static void handle_firmware_event(struct uevent *uevent)
{
    pid_t pid;
    int status;
    int ret;

    if(strcmp(uevent->subsystem, "firmware"))
        return;

    if(strcmp(uevent->action, "add"))
        return;

    /* we fork, to avoid making large memory allocations in init proper */
    pid = fork();
    if (!pid) {
        process_firmware_event(uevent);
        exit(EXIT_SUCCESS);
    } else {
        do {
            ret = waitpid(pid, &status, 0);
        } while (ret == -1 && errno == EINTR);
    }
}

#define UEVENT_MSG_LEN  1024
void handle_device_fd()
{
    char msg[UEVENT_MSG_LEN+2];
    int n;
    while ((n = uevent_checked_recv(device_fd, msg, UEVENT_MSG_LEN)) > 0) {
        if(n >= UEVENT_MSG_LEN)   /* overflow -- discard */
            continue;

        msg[n] = '\0';
        msg[n+1] = '\0';

        struct uevent uevent;
        parse_event(msg, &uevent);

        handle_device_event(&uevent);
        handle_firmware_event(&uevent);
    }
}

/* Coldboot walks parts of the /sys tree and pokes the uevent files
** to cause the kernel to regenerate device add events that happened
** before init's device manager was started
**
** We drain any pending events from the netlink socket every time
** we poke another uevent file to make sure we don't overrun the
** socket's buffer.  
*/

static void do_coldboot(DIR *d)
{
    struct dirent *de;
    int dfd, fd;

    dfd = dirfd(d);

    fd = openat(dfd, "uevent", O_WRONLY);
    if(fd >= 0) {
        write(fd, "add\n", 4);
        close(fd);
        handle_device_fd();
    }

    while((de = readdir(d))) {
        DIR *d2;

        if(de->d_type != DT_DIR || de->d_name[0] == '.')
            continue;

        fd = openat(dfd, de->d_name, O_RDONLY | O_DIRECTORY);
        if(fd < 0)
            continue;

        d2 = fdopendir(fd);
        if(d2 == 0)
            close(fd);
        else {
            do_coldboot(d2);
            closedir(d2);
        }
    }
}

static void coldboot(const char *path)
{
    DIR *d = opendir(path);
    if(d) {
        do_coldboot(d);
        closedir(d);
    }
}

void device_init(void)
{
    suseconds_t t0, t1;
    struct stat info;
    int fd;

    device_fd = open_uevent_socket();
    if(device_fd < 0)
        return;

    fcntl(device_fd, F_SETFD, FD_CLOEXEC);
    fcntl(device_fd, F_SETFL, O_NONBLOCK);

    if (stat(coldboot_done, &info) < 0) {
        t0 = get_usecs();
        coldboot("/sys/class");
        coldboot("/sys/block");
        coldboot("/sys/devices");
        t1 = get_usecs();
        fd = open(coldboot_done, O_WRONLY|O_CREAT, 0000);
        close(fd);
        log_event_print("coldboot %ld uS\n", ((long) (t1 - t0)));
    } else {
        log_event_print("skipping coldboot, already done\n");
    }
}

int get_device_fd()
{
    return device_fd;
}
